1. Field of the Invention
The present invention is generally related to a glare protection device and, more particularly, toward a glare protection device used as a sight window for welding protective masks, helmets, or goggles, for observing welding processes by means of automatic welding machines, or for observing glass or metal melt baths.
2. Description of Related Art
In the case of known glare protection devices of this kind, up to now glass filters with IR and UV reflecting coatings in front of the active electro-optical filter element have been used to achieve the required very high protection against UV and IR radiation. These reflecting filters, however, on the one hand, are very costly and expensive to manufacture and, on the other hand, this front-mounted glass filter is mechanically sensitive and fragile. Accordingly, under the harsh conditions of use a danger of breaking and of splintering is present. In addition to this, small holes (pinholes) in the coating are very difficult to avoid with conventional coating processes. This calls for a costly and time-intensive checking. For this reason, new solutions are sought, in order to overcome these disadvantages.
A different structure is disclosed by U.S. Pat. No. 6,021,520 with a plastic filter plate mounted in front of the active filter element, which contains dyes, in order to absorb both the UV and IR light. This proposal, however, is not suitable for more demanding applications and also is not capable of solving the task set here. The necessary thermal and mechanical stability cannot be achieved with this plastic filter plate. Also the required transparency in the visible region of the spectrum would not be given. If this filter has to absorb both UV and IR light, then in the visible region of the spectrum it would be too dark with the dyes available today to be able to carry out preparation work with protected eyes and to be able to see the welding point immediately before igniting the welding arc, which is absolutely indispensable for a glare protection device according to the invention.
The front-mounted plastic filter plate of U.S. Pat. No. 6,021,520, in principle, is interchangeable so that it may be replaced in the case of degraded characteristics, e.g., in case of distorted optics as a result of thermal-mechanical deformation. This, however, signifies an impermissible risk of handling, because there is the danger that inadvertently an interchangeable plastic filter plate would not be replaced and that thereupon in case of inadvertent use of the glare protection device without this filter serious damage to the eyes of the user could be caused, without the user being in a position to discern this in time (because UV and IR radiation are invisible).